Violet twilight

Study of a violet twilight observed at Pointe-Noire, Congo, Africa, 3 October 1875. Plate 9 from the book Untersuchungen uber Dämmerungserscheinungen zur Erklarung der nach dem Krakatau-ausbruch beobachteten atmospharisch-optischen Storung, by J. Kiessling (Hamburg, Leopold Voss, 1888). The plate is inscribed above: ‘Kiessling, Dämmerung-Untersuchungen. Taf. IX.’ Inscribed below: ‘VIOLETTER DAMMERUNGSSCHEIN ZUR ZEIT DER GRASBRANDE (ABEND). [Violet twilight at the time of the grass fire]. Pechuel-Loesche.Loangokuste, Pontanegra, Oktober 3. 1875. Chromolithographie von Leo Kempner & Co. in Hamburg. Verlag von Leopold Voss in Hamburg (und Leipzig).’ Karl Johann Kiessling (1839-1905) German physicist, replicated twilight glow phenomena in the laboratory. Eduard Moritz Pechuël-Loesche (1840-1913) German naturalist and watercolour painter who travelled widely, including on expeditions to the Congo, Africa.